VIDIOC_QUERYBUF — Query the status of a buffer
|struct v4l2_buffer *argp|
File descriptor returned by
Applications set the
of a struct v4l2_buffer to the same buffer type as was previously used with
type and struct v4l2_requestbuffers
type, and the
field. Valid index numbers range from zero
to the number of buffers allocated with
count) minus one.
fields must be set to 0.
When using the multi-planar API, the
m.planes field must contain a userspace pointer to an
array of struct v4l2_plane and the
length field has
to be set to the number of elements in that array.
VIDIOC_QUERYBUF with a pointer to
this structure drivers return an error code or fill the rest of
flags field the
V4L2_BUF_FLAG_DONE flags will be valid. The
memory field will be set to the current
I/O method. For the single-planar API, the
contains the offset of the buffer from the start of the device memory,
length field its size. For the multi-planar API,
length in the
array elements will be used instead and the
field of struct v4l2_buffer is set to the number of filled-in array elements.
The driver may or may not set the remaining fields and flags, they are
meaningless in this context.
The v4l2_buffer structure is specified in the section called “Buffers”.
On success 0 is returned, on error -1 and the
errno variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.
type is not
supported, or the
index is out of bounds.